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JasonYanHwmartinkpetersen
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scsi: libsas: fix a race condition when smp task timeout
When the lldd is processing the complete sas task in interrupt and set the task stat as SAS_TASK_STATE_DONE, the smp timeout timer is able to be triggered at the same time. And smp_task_timedout() will complete the task wheter the SAS_TASK_STATE_DONE is set or not. Then the sas task may freed before lldd end the interrupt process. Thus a use-after-free will happen. Fix this by calling the complete() only when SAS_TASK_STATE_DONE is not set. And remove the check of the return value of the del_timer(). Once the LLDD sets DONE, it must call task->done(), which will call smp_task_done()->complete() and the task will be completed and freed correctly. Reported-by: chenxiang <chenxiang66@hisilicon.com> Signed-off-by: Jason Yan <yanaijie@huawei.com> CC: John Garry <john.garry@huawei.com> CC: Johannes Thumshirn <jthumshirn@suse.de> CC: Ewan Milne <emilne@redhat.com> CC: Christoph Hellwig <hch@lst.de> CC: Tomas Henzl <thenzl@redhat.com> CC: Dan Williams <dan.j.williams@intel.com> CC: Hannes Reinecke <hare@suse.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Reviewed-by: John Garry <john.garry@huawei.com> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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Diff for: drivers/scsi/libsas/sas_expander.c

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Original file line numberDiff line numberDiff line change
@@ -48,17 +48,16 @@ static void smp_task_timedout(struct timer_list *t)
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unsigned long flags;
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spin_lock_irqsave(&task->task_state_lock, flags);
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if (!(task->task_state_flags & SAS_TASK_STATE_DONE))
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if (!(task->task_state_flags & SAS_TASK_STATE_DONE)) {
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task->task_state_flags |= SAS_TASK_STATE_ABORTED;
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complete(&task->slow_task->completion);
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}
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spin_unlock_irqrestore(&task->task_state_lock, flags);
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complete(&task->slow_task->completion);
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}
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static void smp_task_done(struct sas_task *task)
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{
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if (!del_timer(&task->slow_task->timer))
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return;
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del_timer(&task->slow_task->timer);
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complete(&task->slow_task->completion);
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}
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